The Relation Matrix Method And Its Application Of Water Exchange Study For Sea Bay And Coastal Water

Water exchange is an important hydrodynamic character of sea bay and coastal water, and it is the basis to study the environmental capacity of the water body. There are two main approaches to the study of water exchange. Firstly, based on the assumption that the studied bay is mixing sufficiently, the whole exchange rate or time is calculated by the measured concentration in the bay, out of the bay and at the mouth of the bay, according to the conservation of the water body and the index substance (the salinity is used usually). This method is effective for the bay with small area. Secondly, the distribution of the character time scales of water exchange can be obtained by numerical simulation of water motion.In this dissertation, based on the numerical simulation, the relation matrix is introduced to study the water exchange of sea bay or coastal water with large area. With the study area divided into sub-areas, the element of relation matrix is used to represent the water weighting of certain sub-area contributed by another sub-area, while the relation matrix describe the water exchange relationship among sub-areas. This matrix can be calculated by the results of numerical simulation, and can be considered as the extraction and conclusion of the water exchange character.Variation of water quality due to initial field and source can be predicted by the operation of relation matrix. This method is a simplified model for water quality prediction with simply computation and rapid speed, so it is an effective complement to the complex numerical simulation. In the water quality prediction by relation matrix, the assumption of sufficient mixing is relaxed due to the introduction of the exchange concentration.The conception of residence time is extended from single value to the matrix form which is used to express the time scales of the interaction of water body in the sub-areas. The relation formula of the time scales and the relation matrix is educed. It is pointed out that the residence process and the flushing process characterize the water exchange in Lagrangian viewpoint and Eulerian viewpoint respectively.The hydrodynamic model and the advection-diffusion model are set up to simulate the water exchange. The models are verified by cases with exact solutions and validated against the measured data. In the numerical simulation, a new wetting and drying method based on the"predicted water depth"is developed to deal with the moving boundary due to tidal waves at the tidal flat. In order to validate the new method, test cases are performed. The results show that the new method leads to no excessive numerical wiggles and results in effective estimation of retention volume in each cell with shallow water.The method of relation matrix is verified by a series of typical cases. And it is applied to the water exchange of the Bohai Sea, the Bohai Bay and the Tianjin Coastal Water.